Method for aligning and assembling optical demultiplexer module, and automatic aligning mechanism for optical demultiplexer module

ABSTRACT

The present invention relates to a method of aligning and assembling an optical demultiplexer module having an input fiber, a collimator lens, a diffraction grating, and a photodetector array, and a mechanism for automatically aligning such an optical demultiplexer module. The method comprises the steps of preparing a submodule A including the input fiber and the photodetector array and a submodule B including the diffraction grating and the collimator lens, preparing an alignment jig for allowing the submodules A, B to move independently of each other, fixing the submodules A, B to the adjustment jig, and applying light from the input fiber and moving the submodule B with respect to the submodule A for maximizing a light output from a photodetector.

TECHNICAL FIELD

The present invention relates to a method of aligning and assembling anoptical demultiplexer module for use in the field of opticalcommunications and a mechanism for automatically aligning such anoptical demultiplexer module.

BACKGROUND ART

Optical demultiplexer modules have a function to demultiplexwaveform-multiplexed light, and are capable of receiving a multiplexedlight signal and producing output signals separated in respectivechannels. Generally, input light is introduced from a single opticalfiber into an optical demultiplexer module, which properly separates theinput light into signals of respective channel wavelengths therein, andapplies the signals to a plurality of respective optical fibers orphotodetector devices for respective separate channels, therebyproducing output signals in the respective separate channels.

The wavelength band mainly used in the field of optical communicationsat present is a 1550 nm band with channels separated at frequencyintervals of 100 GHz. If the frequency intervals are expressed in termsof wavelength pitches, then the signals in the channels are arranged atwavelength intervals of about 0.8 nm. An optical demultiplexer module isrequired to angularly separate the signals with a diffraction gratingand apply them accurately to different optical fibers or photodetectordevices in respective channels. Since the wavelength intervals aresmall, the light beams emitted in the respective channels from thediffraction grating have small angular differences.

For assembling an optical demultiplexer module, an active alignmentprocess is carried out by fixing the components thereof in respectivegiven positions such that light having waveforms corresponding torespective channels is introduced from an input fiber and outputtedaccurately from output fibers or photodetector devices. The alignmentprocess needs time, and a very large expenditure of time and labor isrequired to perform the alignment process. Highly accurate and expensiveapparatus are needed to assemble optical demultiplexer modules.

Also, an optical demultiplexer module is made up of many components andis assembled according to a complex assembling procedure. Since it isparticularly necessary to take care of variations in characteristics anddimensions of the components and slight environmental changes, anassembling algorithm is not easy to determine, it is difficult toautomatize the assembling process, as a result of which skilled workersneed to work on the components, resulting in difficulties with the massproduction of optical demultiplexer modules.

If a passive alignment process is employed in lieu of the activealignment process, then errors with respect to dimensions of variouscomponents and devices and assembling errors, represented by thefollowing accuracies, are accumulated:

-   -   (1) the cutting accuracy of the diffraction grating with respect        to the direction of grooves;    -   (2) the mounting accuracy of a photodetector array chip;    -   (3) the accuracy of the package of a photodetector array;    -   (4) the dimensional accuracy of a casing; and    -   (5) the assembling and bonding accuracy of the above components.

It is thus difficult to achieve a desired performance level with thepassive alignment process which depends on abutment of the components,for aligning and assembling optical demultiplexer modules which requirea high level of accuracy.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above problems. Thepresent invention provides a method of aligning and assembling anoptical demultiplexer module to manufacture same highly accurately withease and a mechanism for automatically aligning such an opticaldemultiplexer module. In particular, the present invention provides amethod of aligning and assembling an optical demultiplexer module tomanufacture same with sufficient accuracy in a short period of timewithout using complex equipment and also without the need for skilledpractice, and a mechanism for automatically aligning such an opticaldemultiplexer module.

According to the present invention, a method of aligning and assemblingan optical demultiplexer module having at least an input fiber, acollimator lens, a diffraction grating, and a photodetector array,comprises the steps of:

-   -   (a) preparing a submodule A including the input fiber and the        photodetector array which are fixed in respective positions, and        a submodule B including the diffraction grating and the        collimator lens which are fixed in respective positions;    -   (b) preparing an alignment jig for allowing the submodules A, B        to move independently of each other, and, when the submodules        are held by the alignment jig, adjusting the submodules such        that a reference surface of the submodule A and an alignment        moving direction in which the submodule B is relatively movable        for alignment have a predetermined relationship to each other;    -   (c) fixing the submodule A to the adjustment jig such that a        reference line of the photodetector array lies horizontally;    -   (d) fixing the submodule B to the adjustment jig such that        grooves of the diffraction grating extend vertically; and    -   (e) applying light having a wavelength corresponding to one or        more channels from the input fiber, moving the submodule B with        respect to the submodule A to align the submodules for        maximizing a light output from a photodetector corresponding to        the channel or channels.

The submodule B further includes first and second tubes slidable againsteach other, the collimator lens and the diffraction grating being fixedto the second tube, and the method further comprises the step of (f)bringing the first tube as an adjustment tube into sliding contact withthe second tube while the second tube is being fixed, and bonding thesubmodules A, B to each other, so as to hold a positioning relationshipbetween the submodules A, B after the step (e).

The alignment moving direction is a direction Z along which thesubmodules A, B are movable toward and away from each other, and thepredetermined relationship is a relationship in which the referencesurface of the submodule A and the alignment moving direction of thesubmodule B are perpendicularly to each other. Alternatively, thealignment moving direction is a direction X along which the submodulesA, B are movable horizontally parallel to each other, and thepredetermined relationship is a relationship in which the referencesurface of the submodule A and the alignment moving direction of thesubmodule B are parallel to each other. Alternatively, the alignmentmoving direction is a direction Y along which the submodules A, B aremovable vertically parallel to each other, and the predeterminedrelationship is a relationship in which the reference surface of thesubmodule A and the alignment moving direction of the submodule B areparallel to each other. Further alternatively, the alignment movingdirection is a direction z around an optical axis of the submodule B,and the predetermined relationship is a relationship in which thesubmodule B is angularly displaceable with respect to the referencesurface of the submodule A.

More preferably, the alignment moving direction includes a direction Zalong which the submodules A, B are movable toward and away from eachother, a direction X along which the submodules A, B are movablehorizontally parallel to each other, a direction Y along which thesubmodules A, B are movable vertically parallel to each other, and adirection z around an optical axis of the submodule B, the step (e)comprising the step of successively moving the submodules A, Bsuccessively in the directions Z, X, Y, z to maximize light outputs inthe respective directions.

According to the present invention, there is also provided a mechanismfor automatizing an aligning process when an optical demultiplexermodule is assembled. The optical demultiplexer module has a submodule Aincluding an input fiber and a photodetector array which are fixed inrespective positions, and a submodule B including a diffraction gratingand a collimator lens which are fixed respective positions. Themechanism comprises:

-   -   a fixed table;    -   a first movable unit mounted on the fixed table and movable in a        first moving direction with respect to the fixed table by a        first motor which is installed on the first movable unit;    -   a second movable unit mounted on the first movable unit and        movable in a second moving direction with respect to the first        movable unit by a second motor which is installed on the second        movable unit;    -   a first support vertically fixed to the second movable unit;    -   a third movable unit mounted on the first support and movable in        a third direction with respect to the first support by a third        motor which is installed on the third movable unit, the third        movable unit having gripping means for gripping the submodule B;    -   a rotary actuator unit mounted on the third movable unit for        gripping and rotating the submodule B on the third movable unit        with a fourth motor which is installed on the rotary actuator        unit;    -   a second support vertically fixed to the fixed table for        supporting the submodule A fixedly thereon;    -   a light source for introducing light of an arbitrary wavelength        into the optical fiber; and    -   a computer system for controlling the first through fourth        motors to move the submodule B with respect to the submodule A        to maximize an optical output from the photodetector array which        detects a light beam applied from the submodule A through the        input fiber and reflected and focused by the collimator lens and        the diffraction grating of the submodule B.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a completed optical demodulatormodule according to the present invention;

FIG. 2 is a partial exploded perspective view of an optical demodulatormodule shown as divided into two submodules in a method of aligning andassembling an optical demultiplexer module according to a firstembodiment of the present invention; and

FIG. 3 is a schematic side elevational view of a mechanism forautomatically aligning an optical demultiplexer module according to asecond embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A basic arrangement of an optical demultiplexer module according to thepresent invention will first be described below with reference to aperspective view of FIG. 1.

An optical demultiplexer module 100 according to the present inventioncomprises a single input optical fiber 1, a collimator lens 2, and adiffraction grating 3 as components, and has a plurality of transparentor semitransparent tubes 51, 52, 53 (though three tubes are shown in theillustrated example, any desired number of tubes may be used) which areindependent of each other with the above components bonded or fixedthereto, the tubes having such inside and outside diameters that theyare interfitted and slidable axially.

An external input is introduced from the optical fiber 1 into the tubes,and a divergent light beam 101 spreading depending on the numericalaperture of the fiber reaches the collimator lens 2, which converts thedivergent light beam 101 into a parallel light beam that reaches thediffraction grating 3. The light beam is separated into light beams ofrespective wavelengths by the diffraction grating 3 depending on thechromatic dispersion characteristics of the diffraction grating 3. Thelight beams are then converted into respective convergent light beams104 of respective demultiplexed wavelengths by the collimator lens 2.The convergent light beams 104 are focused on one surface of a sideplate 50 (transparent glass disk member) which is positioned at thefocal point of the collimator lens 2, and are arranged as an array ofbeam spots on the one surface of the side plate 50. The input fiber 1has an open end positioned by a fiber joint 10 on the one surface of theside plate 50 which lies on the focal plane of the collimator lens 2.The diffraction grating 3 is mounted on an inner surface of a side plate54 (disk member) fixed to an end of the tube 53. The diffraction grating3 is disposed at such an angle to reflect diffracted light beamsproduced from the light beam introduced from the input fiber 1 andapplied from the collimator lens 2, back toward the collimator lens 2,which focuses the light beams onto the focal plane of the collimatorlens 2. The focused beam spots produced on the focal plane by thedemultiplexed light beams of the respective wavelengths are monitored ordetected by a photodetector array or fiber array 4 which is bonded orfixed in a position that is conjugate to the input fiber 1 on the focalplane on the one surface of the side plate 50, and which is mounted inan independent sealed package.

The optical demultiplexer module 100 includes roughly three tubes,preferably hollow cylindrical tubes 51, 52, 53. The single-core inputfiber 1 is fixed to an end face (left end face in FIG. 1) of the tube 51which is transparent for mounting the fiber thereon, by the fiber-fixingside plate 50 and the fiber joint 10. Similarly, the collimator lens 2is fixed to an end face (right end face in FIG. 1) of the tube 52. Thediffraction grating 3 is fixed to an end face (right end face in FIG. 1)of the tube 53 by the diffraction grating fixing side plate 54. In thisembodiment, the tubes 52, 53 are integrally joined to each other as byadhesive bonding after the collimator lens 2 is fixed to the end face ofthe tube 52. The end of the tube 52 is fitted in the tube 51 as anadjustment tube. The outside diameter of the tube 52 and the insidediameter of the tube 51 are dimensioned such that the tubes 51, 52 areslidable against each other without play therebetween so that they aremovable along and rotatable around the optical axis.

A specific process of aligning and assembling the optical demultiplexermodule described above will be described below.

<1st Step>

For aligning and assembling the optical demultiplexer module, twosubmodules A, B, described below, are prepared, and components are fixedin position within the submodules A, B.

Submodule A: This includes the optical fiber 1 and the photodetectorarray (PDA) 4 that are fixed in position on one surface of the sideplate (transparent glass disk) 50.

Submodule B: This includes the diffraction grating 3 that is fixed inposition on one surface of the diffraction grating fixing side plate 54,and the collimator lens 2. The collimator lens 2 is fixed to one end ofthe tube 52, and encased in the distal end of the tube 53. After thecollimator lens 2 fixed to one end of the tube 52 is encased in the tube53, the tubes 52, 53 are fixed to each other by an adhesive or the like.At this time, the tube 51 as an adjustment tube for connecting thesubmodules A, B is not fixed to the tube 52.

<2nd Step>

The submodules A, B are then aligned with each other by an activealignment process as follows:

-   -   1st substep: An alignment jig for allowing the submodules A, B        to move independently of each other is prepared. The submodules        A, B are held by the alignment jig. At this time, the submodules        A, B are adjusted such that the direction indicated by the arrow        Z along which the submodule B is moved for alignment is        perpendicular to a surface (reference surface) of the side plate        50 of the submodule A which is opposite to the surface to which        the optical fiber 1 and the PDA 4 are fixed.    -   2nd substep: Then, the submodule A is fixed to the alignment jig        such that the PDA 4 has its reference line (along the array of        photodetectors) extending horizontally.    -   3rd substep: The submodule B is fixed to the alignment jig such        that the grooves of the diffraction grating 3 extend vertically.    -   4th substep: Thereafter, a light beam having a waveform        corresponding to one channel is introduced from the optical        fiber 1, and the submodule B is moved for alignment (active        alignment) to maximize an output signal from the photodetector        of the photodetector array 4 which corresponds to the channel.    -   5th substep: If necessary, the above 4th substep is carried out        for a different wavelength (channel).    -   6th substep: After the alignment process is completed, the        submodules A, B are bonded to each other in their established        positional relationship, using the adjustment tube (tube 51).

The submodule B is constructed of the two tubes 52, 53 as cylindricalcasings, the side plate 54, and the collimator lens 2 and thediffraction grating 3 which are fixed to the tubes 52, 53 and the sideplate 54. The diffraction grating 3 is fixed to the inner surface of theside plate 54 at a position slightly offset from the central axis of thetube 53, the diffraction grating 3 being inclined at a predeterminedangle to the surface of the side plate 54. The collimator lens 2 isfixed to the end of the tube 52. The tubes 52, 53 are fixed to eachother with the collimator lens 2 and the diffraction grating 3 beingspaced from each other by a predetermined distance. On the submodule A,the end of the optical fiber 1 (as supported by the fiber joint 10) andthe PDA 4 are fixed in a positional relationship of certain accuracywith respect to each other within one surface (the one surface of theside plate 50). The submodule B can be aligned with the submodule Awithin a range represented by an angular interval z₁ around the opticalaxis Z, a distance z₂ along the optical axis Z, and distances x, y indirections perpendicular to the optical axis Z. The submodules A, B arefinally fixed to each other by bonding the circular side plate 50 of thesubmodule A, which has a slightly larger diameter than the outsidediameter of the adjustment tube 51, to the distal end of the adjustmenttube 51 while keeping the circular side plate 50 in its adjustedposition based on the distances x, y, and bonding the adjustment tube51, which has an inside diameter allowing the adjustment tube 51 toslidingly fit over the distal end of the tube 52 of the submodule B, tothe tube 52 while keeping the adjustment tube 51 in its adjustedposition based on the angular interval z₁ and the distance z₂. Theadjustment tube 51 needs to have a length larger than the distancebetween the inner flat surface of the circular side plate 50 of thesubmodule A and the distal end of the submodule B (the tube 52) in thefinally aligned position based on the distance z₂.

An automatic aligning mechanism according to a second embodiment of thepresent invention will be described below. FIG. 3 shows in schematicside elevation an automatic aligning mechanism 200 according to a secondembodiment of the present invention. As shown in FIG. 3, the automaticaligning mechanism 200 comprises a fixed table 201, a first movable unit202 mounted on the fixed table 201 and movable in the directionindicated by the arrow Z (left and right directions on the sheet of FIG.3) with respect to the fixed table 201 by a motor MZ which is installedon the first movable unit 202, a second movable unit 203 mounted on thefirst movable unit 202 and movable in the direction indicated by thearrow X (normal to the sheet of FIG. 3) with respect to the firstmovable unit 202 by a motor MX which is installed on the second movableunit 203, a first support 204 vertically fixed to the second movableunit 203, a third movable unit 205 mounted on the first support 204 andmovable in the direction indicated by the arrow Y (vertical direction)with respect to the first support 204 by a motor MY which is installedon the third movable unit 205, a rotary actuator unit 206 mounted on thethird movable unit 205 for gripping and rotating the submodule B throughthe angular interval z₁ about its own axis with a motor M z₁ which isinstalled on the rotary actuator unit 206, and a second support 207vertically fixed to the fixed table 201 for supporting the submodule Afixedly thereon.

The automatic aligning mechanism 200 also has a computer 211. Thecomputer 211 outputs an adjustment signal for adjusting the output powerof a light source 208 through a signal line 213 to the light source 208to enable the light source 208 to introduce input light through anoptical fiber 209 into an optical demultiplexer module. The computer 211receives output signals from the respective photodetectors of the PDA 4of the submodule A through an amplifier 210, monitors the output signalsfrom the respective photodetectors as indicated by 212, controls themotors with respective motor driver circuits (not shown) to maximize theoutput signals from the respective photodetectors (to maximize the lightintensities), and controls the power of the input light introducedthrough the optical fiber 209. The motor driver circuits are omittedfrom illustration in FIG. 3.

Prior to an automatic alignment process, the submodule A (the circularside plate 50) is fixed to the second support 207. The submodule A isnot moved during the automatic alignment process. However, the circularside plate 50 needs to be preadjusted so as to lie parallel to the endface of the submodule B. The circular side plate 50 may be preadjustedby a known adjustment mechanism, which is not shown. All movingmechanisms of the automatic aligning mechanism 200 are associated withthe submodule B for moving the submodule B, in which the V grooves ofthe diffraction grating 3 are held vertically, in the directions X, Y, Zand z for alignment.

With the automatic aligning mechanism 200, the various movable unitswhich are capable of making adjustments identical to those illustratedin the first embodiment are actuated by the motors to performcorresponding scanning processes. Initially, the light source 208 is setto a high intensity level, and introduces light of an arbitrarywavelength through the optical fiber 208 into the submodule B. A givenchannel in the PDA 4 of the submodule A is monitored, and the submoduleB is scanned in the direction Z in order to determine a position wherethe output of the PDA 4 is maximum. The submodule B is scanneddigitally, and the motor MZ is de-energized at a position where thelight output is maximum. Then, the submodule B is operated in thedirections X, Y by the motors MX, MY (or may be operated in anothersequence). The above operation is repeated to determine positions wherethe light output is maximum (light intensity is maximum) in therespective directions. The adjustment through the angular interval z₁mainly serves to adjust the direction of the PDA 4. Wavelengths arechanged, and the above aligning operation is repeated on thephotodetectors of the PDA 4 in different channels to determined theoptical position in the direction z.

After the above alignment process is completed, the adjustment tube 51is moved into contact with the submodule A, and then temporarily fixedthereto. To fix the adjustment tube 51 to the submodule A, anultraviolet-curable resin is dropped, and then an ultraviolet lightsource is turned on to apply ultraviolet radiation to cure theultraviolet-curable resin. Since only the ultraviolet-curable resin isunable to provide sufficient bonding strength, after the temporarilyfixed module is removed from the automatic aligning mechanism, it isreinforced by a desired adhesive which is curable at normal temperature.Heat-curable adhesives are not preferable as they would degrade andmodify the PDA 4, etc.

According to a modification within a scope for achieving the object ofthe present invention, the separable regions of the opticaldemultiplexer module are not limited to those in the above embodiments.The same method as described above is applicable to optical systemswhich need alignment. For example, the same method is applicable to anoptical demultiplexer module which employs an optical fiber array or anoptical waveguide array instead of the PDA, and also to an opticalswitch or an optical modulator which employs a reflecting mirror, otherthan an optical demultiplexer module, or a semiconductor laser or alight source module using a semiconductor laser array.

INDUSTRIAL APPLICABILITY

According to the present invention, since an optical demultiplexermodule is constructed of two separate submodules, it can easily bealigned and assembled for increased productivity. Each of the submodulesmay be assembled with a level of accuracy that can be achieved byabutment of component profiles. Therefore, no skilled practice isrequired, and the assembling process may be automatized. Opticaldemultiplexer modules for use in the field of optical communications canthus be mass-produced with high accuracy.

1. A method of aligning and assembling an optical demultiplexer modulehaving at least an input fiber, a collimator lens, a diffractiongrating, and a photodetector array, comprising the steps of: (a)preparing a submodule A including said input fiber and saidphotodetector array which are fixed in respective positions, and asubmodule B including said diffraction grating and said collimator lenswhich are fixed in respective positions; (b) preparing an alignment jigfor allowing said submodules A, B to move independently of each other,and, when the submodules are held by said alignment jig, adjusting thesubmodules such that a reference surface of said submodule A and analignment moving direction in which said submodule B is relativelymovable for alignment have a predetermined relationship to each other;(c) fixing said submodule A to said adjustment jig such that a referenceline of said photodetector array lies horizontally; (d) fixing saidsubmodule B to said adjustment jig such that grooves of said diffractiongrating extend vertically; and (e) applying light having a wavelengthcorresponding to one or more channels from said input fiber, and movingsaid submodule B with respect to said submodule A to align thesubmodules for maximizing a light output from a photodetectorcorresponding to said channel or channels.
 2. A method according toclaim 1, wherein said submodule B further includes first and secondtubes slidable against each other, said collimator lens and saiddiffraction grating being fixed to said second tube, said method furthercomprising the step of: (f) bringing said first tube as an adjustmenttube into sliding contact with said second tube while said second tubeis being fixed, and bonding said submodules A, B to each other, so as tohold a positioning relationship between said submodules A, B after saidstep (e).
 3. A method according to claim 1, wherein said alignmentmoving direction is a direction Z along which said submodules A, B aremovable toward and away from each other, and said predeterminedrelationship is a relationship in which said reference surface of saidsubmodule A and said alignment moving direction of said submodule B areperpendicular to each other.
 4. A method according to claim 1, whereinsaid alignment moving direction is a direction X along which saidsubmodules A, B are movable horizontally parallel to each other, andsaid predetermined relationship is a relationship in which saidreference surface of said submodule A and said alignment movingdirection of said submodule B are parallel to each other.
 5. A methodaccording to claim 1, wherein said alignment moving direction is adirection Y along which said submodules A, B are movable verticallyparallel to each other, and said predetermined relationship is arelationship in which said reference surface of said submodule A andsaid alignment moving direction of said submodule B are parallel to eachother.
 6. A method according to claim 1, wherein said alignment movingdirection is a direction z around an optical axis of said submodule B,and said predetermined relationship is a relationship in which saidsubmodule B is angularly displaceable with respect to said referencesurface of said submodule A.
 7. A method according to claim 1, whereinsaid alignment moving direction includes a direction Z along which saidsubmodules A, B are movable toward and away from each other, a directionX along which said submodules A, B are movable horizontally parallel toeach other, a direction Y along which said submodules A, B are movablevertically parallel to each other, and a direction z around an opticalaxis of said submodule B, said step (e) comprising the step ofsuccessively moving the submodules A, B successively in the directionsZ, X, Y, z to maximize light outputs in the respective directions.
 8. Amechanism for automatically aligning an optical demultiplexer modulehaving a submodule A including an input fiber and a photodetector arraywhich are fixed in respective positions, and a submodule B including adiffraction grating and a collimator lens which are fixed in respectivepositions, said mechanism comprising: a fixed table; a first movableunit mounted on said fixed table and movable in a first moving directionwith respect to said fixed table by a first motor which is installed onthe first movable unit; a second movable unit mounted on said firstmovable unit and movable in a second moving direction with respect tosaid first movable unit by a second motor which is installed on thesecond movable unit; a first support vertically fixed to said secondmovable unit; a third movable unit mounted on said first support andmovable in a third direction with respect to said first support by athird motor which is installed on the third movable unit, said thirdmovable unit having gripping means for gripping said submodule B; arotary actuator unit mounted on said third movable unit for gripping androtating said submodule B on said third movable unit with a fourth motorwhich is installed on said rotary actuator unit; a second supportvertically fixed to said fixed table for supporting said submodule Afixedly thereon; a light source for introducing light of an arbitrarywavelength into said optical fiber; and a computer system forcontrolling said first through fourth motors to move said submodule Bwith respect to said submodule A to maximize an optical output from saidphotodetector array which detects a light beam applied from saidsubmodule A through said input fiber and reflected and focused by saidcollimator lens and said diffraction grating of said submodule B.
 9. Amechanism according to claim 8, wherein said first moving direction is adirection Z along which said submodule B gripped by said rotary actuatorunit is movable toward and away from said submodule A in an axialdirection with respect to a reference surface of said submodule A whichis fixed to said second support.
 10. A mechanism according to claim 8,wherein said second moving direction is a direction X along which saidsubmodule B gripped by said rotary actuator unit is movable horizontallyparallel to a reference surface of said submodule A which is fixed tosaid second support.
 11. A mechanism according to claim 8, wherein saidthird moving direction is a direction Y along which said submodule Bgripped by said rotary actuator unit is movable vertically parallel to areference surface of said submodule A which is fixed to said secondsupport.
 12. A mechanism according to claim 8, wherein a direction inwhich said submodule B gripped by said rotary actuator unit is grippedand rotated on said third movable unit is a direction about an axis ofsaid submodule B.